Method of treating toxic aromatic halogen-containing compounds by electrophilic aromatic substitution

Abstract

An improved method for detoxifying waste materials contaminated with halogenated aromatic hydrocarbons is disclosed. The method provides for detoxification of halogenated aromatic compounds by electrophilic aromatic substitution. The method also provides for the dehalogenation of the lower congeners of such halogenated aromatic compounds, as a result of chemical activation via electrophilic aromatic substitution, followed by nucleophilic aromatic dehalogenation. In addition, the method provides for the more complete dehalogenation of mixtures of halogenated aromatic compounds that contain both higher and lower congeners by increasing the efficiency of dehalogenation of the lower congeners.

We claim: 
     
       1. A method for treating a waste material comprising a halogenated aromatic compound, the method comprising the step of incubating a reaction mixture at a temperature and for a period of time sufficient to form an electrophilically substituted halogenated aromatic compound, the reaction mixture comprising the waste material and an electrophilic aromatic substitution reagent selected from the group consisting of mixtures of POCl 3  and trifluoromethanesulfonic acid; mixtures of HNO 3  and H 2  SO 4  ; mixtures of dimethylformamide and POCl 3  ; H 2  SO 4  ; mixtures of ClSO 3  H; mixtures of H 2  SO 4  SO 3  ; mixtures of H 2  SO 3  ; mixtures of RX and a member selected from the group consisting of AlCl 3 , FeCl 3  and BF 3 , wherein R is a straight or branched chain alkyl group between C 1  and C 20  and X is a halogen; and mixtures of R 1  COCl and a member selected from the group consisting of AlCl 3 , FeCl 3  and BF 3 , wherein R 1  is a straight or branched chain alkyl group between C 1  and C 20  or an aryl group, the reagent being present in an amount sufficient to electrophilically substitute the halogenated compound, wherein a halogen atom of the halogenated aromatic compound is electrophilically substituted by a non-halogen group of the electrophilic aromatic substitution reagent, and wherein the halogenated compound is dehalogenated thereby. 
     
     
       2. The method according to claim 1 wherein the halogenated aromatic compound is selected from the group consisting of PCBs, PCDDs, PCDFs and mono- and dichlorobenzene. 
     
     
       3. The method according to claim 2 wherein the number of halogen atoms contained in the compound is less than or equal to 4. 
     
     
       4. The method according to claim 1 wherein the electrophilic aromatic substitution reagent comprises sulfuric acid. 
     
     
       5. The method according to claim 1 wherein the electrophilic aromatic substitution reagent comprises a mixture of sulfuric acid and chlorosulfonic acid. 
     
     
       6. The method according to claim 1 wherein the electrophilic aromatic substitution reagent comprises a mixture of sulfuric acid and SO 3 . 
     
     
       7. A method for forming a substituted halogenated aromatic compound, comprising the step of incubating a reaction mixture at a temperature and for a period of time sufficient to form an electrophilically substituted halogenated aromatic compound, the reaction mixture comprising the halogenated aromatic compound and an electrophilic aromatic substitution reagent selected form the group consisting of mixtures of POCl 3  and trifluoromethanesulfonic acid; mixtures of dimethylformamide and POCl 3  ; mixtures of RX and a member selected from the group consisting of AlCl 3 , FeCl 3  and BF 3 , wherein R is a straight or branched chain alkyl group between C 1  and C 20  and X is a halogen; mixtures of R 1  COCl and a member selected from the group consisting of AlCl 3 , FeCl 3  and BF 3 , wherein R 1  is a straight or branched chain alkyl group between C 1  and C 20  or an aryl group; and mixtures of X 2  and FeCl 3 , wherein X is any halogen, the reagent being present in an amount sufficient to electrophilically substitute the halogenated compound, wherein a halogen atom of the halogenated aromatic compound is electrophilically substituted by a non-halogen group of the electrophilic aromatic substitution reagent, and wherein the halogenated compound is dehalogenated thereby. 
     
     
       8. The method according to claim 7 wherein the halogenated aromatic compound is selected from the group consisting of PCBs, PCDDs, and PCDFs. 
     
     
       9. The method according to claim 7 wherein the number of halogen atoms contained in the compound is less than or equal to 4.